Sorry for the delay. I saw the posting this morning, but have been tying to keep the plates spinning on the end of sticks today. Life can get in the way sometimes!
There are vintage bike fans here in Colorado, but we are scattered throughout the state. Colorado is a good size state and organizing a ride takes some longer range planning. For example, Durango is 6.5 hour drive to Denver. I have a friend in Carbondale Colorado who is a vintage bike fan and collector. There is a vintage bike ride in June in Parker, CO called the Eddy Rando. The event is organize/run by Kirk Webster who runs Creekside Bicycle Shop. Kirk is a good guy and vintage bike fan. I have copied and pasted the website link below. I have only been able to attend the Eddy Rando once over the last 4 years with the pandemic and other family matters getting in the way, but I hope to attend next year. As I remember there are two rides in the event, plus a nice bike show/concours, and lunch is usually provided. It is a good day out.
http://creeksidesteelcycling.com/events.html
Again, prior to the pandemic, I organized a monthly classic bike ride in Durango, and I would typically get 10 to 12 people to attend. The problem I found is that the range of abilities was really wide making it hard to keep the group together. I haven't been able to organize monthly rides this year. However, I have a handful of friends in Durango that are vintage/classic bicycle fans and I ride with them regularly. I also ride with people on plastic bikes and my old bikes are usually the topic of conversation. We have to continue to foster converts to our cause! I have attached one of my flyers I distributed around town. As we come into the fall, I may try to organize some steel rides next year. We will see what happens.
I think reaching out on Bikeforums C&V is a good start, but I would work with your local bike shop and see if they can connect you with some locals that ride classic bikes. Or see if they would let you post a flyer in the shop window? Most classic bike fans out there don't know about Bikeforums. You might also join ClassicRendezvous (CR) and post a message saying where you live in the Denver metro area and see what kind of response you get. I know there are quite a few CR members spread out from Fort Collins to Colorado Springs at a minimum.
Another event worth considering is the Sante Fe New Mexico Century ride weekend. They have a 25, 50, and 100 mile rides. On Saturday afternoon they have a classic bike show/concours, which I have participated in twice. My son got a ribbon one year and I got second place in 2021. Google Sante Fe Century.
Second Place for 1963 Masi Special at Sante Fe Century
Flyer I posted at local businesses throughout Durango.